Bluebottles have surged ashore in large numbers on the New South Wales Mid North Coast, amid continued wet and windy weather.
The bluebottle jellyfish have been seen in a thick mass along the tide line at Port Macquarie beaches in recent days, and further south at beaches near Taree and Forster.
Bluebottles are essentially at the mercy of the wind and ocean currents and often wash ashore during summer months after north-easterly winds.
Shane Ahyong, from the Australian Museum, said bluebottles did not actively swim.
"Instead, they rely on their crest that acts like a sail to catch the wind or they get transported by the ocean current," Dr Ahyong said.
"That's why during and after windy weather, especially with onshore winds, bluebottles are often washed up along the beach."
Beachgoers are urged to be careful if they spot bluebottles on the beach as their tentacles can still sting.
"If you get to the beach and see that thousands of bluebottles have been washed up, it is best to avoid going into the water. If you must go swimming, wear protective clothing," Dr Ahyong said.
The Australian Museum recommends if a person is stung, any remaining stinging cells are washed off with salt water. Hot water can then be applied to reduce the discomfort.
If symptoms remain, or if the sting occurs around the face or throat, medical help should be sought immediately.
Debris in the water
The jellyfish warning comes amid wild weather along the northern New South Wales coast.
Mid North Coast residents living along waterways are being urged to secure vessels and belongings, as flood warnings remain in the region.
According to Marine Rescue Port Macquarie, the majority of boaties have heeded the recent advice and warnings.
"There's only been very few boats going out in these conditions, they've been quite good," unit commander Greg Davies said.
"There is a lot of debris in the water, especially in the barrier, there've been a few logs and trees."
'Secure your vessels'
Bluebottles are not the only thing washing ashore with a sailing boat triggering a hazardous material incident when it landed on Pilot Beach, south of Port Macquarie, on Monday.
Fire and Rescue NSW said the vessel was carrying 300 litres of diesel fuel, which crews worked to decant into recovery bins, and 60 litres of oil.
Mr Davies asked people in the area to prepare and keep across further warnings from the Bureau of Meteorology and State Emergency Service.
"Just make sure all vessels on moorings are secure and watertight so that they don't flood with water," he said.
